Strange error code appearing in empty sub categories (5 posts)

Warning: Invalid argument supplied for foreach() in /home/prepayas/public_html/blog/wp-includes/query.php on line 2746

Here is my blog blog.pre-pay-as-you-go.co.uk to view the error in the main silver navigation bar go to Videos and choose Handset Videos/Apple or alternatively Mobile gaming and then Windows phone 7 games

To be honest I dont understand PHP all to well so I know I havent done anything within the query-php include file. In fact when I found the file in Cpanel file manager it says the file was last updated on the 29th of December.

Here's the code I think the error is refering to with line 2746 beginning with foreach.